package org.freeocs.dispatcher;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.zip.GZIPOutputStream;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

import org.freeocs.commons.util.RequestUtils;

/**
 * 数据压缩过滤器
 * 
 * @author chirs
 */
public class FOCSGZIPFilter implements Filter {

	private List<String> ignore_pages = new ArrayList<String>();

	@SuppressWarnings("unchecked")
	public void init(FilterConfig filterConfig) {
		Enumeration pnames = filterConfig.getInitParameterNames();
		while (pnames.hasMoreElements()) {
			String param = (String) pnames.nextElement();
			if (param.startsWith("ignore")) {
				ignore_pages.add(filterConfig.getInitParameter(param));
			}
		}
	}

	public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
		if (req instanceof HttpServletRequest) {
			HttpServletRequest request = (HttpServletRequest) req;
			HttpServletResponse response = (HttpServletResponse) res;
			try {
				String uri = request.getRequestURI().substring(request.getContextPath().length());
				boolean ignore = ignore_pages.contains(uri);
				if (!ignore && isGZIPSupported(request)) {
					GZIPResponseWrapper wrappedResponse = new GZIPResponseWrapper(response);
					chain.doFilter(req, wrappedResponse);
					wrappedResponse.finishResponse();
					return;
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		chain.doFilter(req, res);
	}

	/**
	 * 判断浏览器是否支持GZIP压缩
	 * 
	 * @param req
	 * @return
	 */
	private boolean isGZIPSupported(HttpServletRequest req) {
		String browserEncodings = RequestUtils.getHeader(req, "accept-encoding");
		return ((browserEncodings != null) && (browserEncodings.indexOf("gzip") != -1));
	}

	public void destroy() {
		if (ignore_pages != null) {
			ignore_pages.clear();
			ignore_pages = null;
		}
	}
}

/**
 * GZIP流
 * 
 * @author chirs
 */
class GZIPResponseStream extends ServletOutputStream {

	protected ByteArrayOutputStream baos = null;

	protected GZIPOutputStream gzipstream = null;

	protected boolean closed = false;

	protected HttpServletResponse response = null;

	protected ServletOutputStream output = null;

	public GZIPResponseStream(HttpServletResponse response) throws IOException {
		super();
		closed = false;
		this.response = response;
		this.output = response.getOutputStream();
		baos = new ByteArrayOutputStream();
		gzipstream = new GZIPOutputStream(baos);
	}

	public void close() throws IOException {
		if (closed) {
			throw new IOException("This output stream has already been closed");
		}
		gzipstream.finish();

		byte[] bytes = baos.toByteArray();

		response.addHeader("Content-Length", Integer.toString(bytes.length));
		response.addHeader("Content-Encoding", "gzip");
		output.write(bytes);
		output.flush();
		output.close();
		closed = true;
	}

	public void flush() throws IOException {
		if (closed) {
			throw new IOException("Cannot flush a closed output stream");
		}
		gzipstream.flush();
	}

	public void write(int b) throws IOException {
		if (closed) {
			throw new IOException("Cannot write to a closed output stream");
		}
		gzipstream.write((byte) b);
	}

	public void write(byte b[]) throws IOException {
		write(b, 0, b.length);
	}

	public void write(byte b[], int off, int len) throws IOException {
		if (closed) {
			throw new IOException("Cannot write to a closed output stream");
		}
		gzipstream.write(b, off, len);
	}

	public boolean closed() {
		return (this.closed);
	}

	public void reset() {

	}
}

/**
 * GZIP的Response封装
 * 
 * @author chirs
 */
class GZIPResponseWrapper extends HttpServletResponseWrapper {
	protected HttpServletResponse origResponse = null;

	protected ServletOutputStream stream = null;

	protected PrintWriter writer = null;

	public GZIPResponseWrapper(HttpServletResponse response) {
		super(response);
		origResponse = response;
	}

	public ServletOutputStream createOutputStream() throws IOException {
		return (new GZIPResponseStream(origResponse));
	}

	public void finishResponse() {
		try {
			if (writer != null) {
				writer.close();
			} else {
				if (stream != null) {
					stream.close();
				}
			}
		} catch (IOException e) {
		}
	}

	public void flushBuffer() throws IOException {
		stream.flush();
	}

	public ServletOutputStream getOutputStream() throws IOException {
		if (writer != null) {
			throw new IllegalStateException("getWriter() has already been called!");
		}

		if (stream == null)
			stream = createOutputStream();
		return (stream);
	}

	public PrintWriter getWriter() throws IOException {
		if (writer != null) {
			return (writer);
		}

		if (stream != null) {
			throw new IllegalStateException("getOutputStream() has already been called!");
		}

		stream = createOutputStream();
		writer = new PrintWriter(new OutputStreamWriter(stream, "UTF-8"));
		return (writer);
	}

	public void setContentLength(int length) {
	}

}